Tiffany ate 3 slices of cake. Christopher ate 4 slices. If Tiffany ate $\dfrac{3}{10}$ of the cake, what fraction of the cake is remaining?
Solution: If 3 slices represent $\dfrac{3}{10}$ of the cake, there must have been a total of 10 slices. $\text{fraction of cake remaining} = \dfrac{\text{number of slices remaining}}{\text{number of slices total}}$ Together they ate 7 slices, which leaves 3 out of 10 slices remaining. There is $\dfrac{3}{10}$ of the cake remaining.